Medical devices may be surgically implanted within a patient and may include devices such as cardiac pacemakers, defibrillators, neurostimulators, and cardiac monitors. These implantable medical devices typically include a hermetically-sealed metal case including circuitry for generating electrical signals that are delivered to the patient's heart through one or more conductors that pass from the interior of the can to the exterior of the can through a feedthrough assembly that includes the hermetic seal. This hermetic seal serves to isolate the circuitry within the metal case from tissue, blood, and other patient fluid.
In addition to the electrical signals generated by the circuitry of the implantable medical device, externally generated electromagnetic signals can also pass through the hermetic seal via the feedthrough assembly and interfere with proper operation of the implantable medical device. Thus, electromagnetic interference filters are often integrated into implantable medical devices to filter these externally generated electromagnetic signals to maintain the intended voltage levels along the conductors. The electromagnetic filters typically include complex multilayer laminated capacitors that are configured to filter external signals of hundreds of volts and are therefore often quite expensive, which may increase the cost of the implantable medical device as a whole. Thus, there is a need for improved filtered feedthrough assemblies for implantable medical devices.